1. Technical Field
The present invention relates to a photomask, on which a pattern is formed with a light shielding material, for transferring the pattern to a photoresist with light passed through the photomask, a method of manufacturing the photomask, and an exposure apparatus.
2. Description of Related Art
In recent years, for a display apparatus displaying a picture and an image, a liquid crystal display panel using a TFT (Thin Film Transistor) for example has widely been used. Also, a technique of photolithography is often used in manufacturing a liquid crystal display panel, a semiconductor device, a printed substrate and the like.
A photolithography is a technique of transferring and developing a pattern formed on a photomask on a substrate by irradiating light from a light source onto the substrate through the photomask after applying a photoresist on the substrate. On the photomask, a predetermined pattern to be transferred to the substrate is formed with a light shielding material. Therefore, the predetermined pattern is transferred on the substrate by irradiating light passed through areas other than the predetermined pattern to the substrate.
In exposure processing in which light from a light source is irradiated onto a substrate through a photomask, the photomask is expanded (deformed) due to heat from the light source. Accordingly, even when the same photomask is used, a difference occurs in patterns transferred on the substrate depending on the degree of expansion of the photomask, which may cause exposure flaws.
Therefore, Japanese Patent Application Laid-Open No. 2010-182942 proposes a technique of configuring, in a stage device for holding a photomask, a surface being in contact with a photomask using a plurality of materials having coefficients of thermal expansion different from each other. Japanese Patent Application Laid-Open No. 2010-182942 also proposes a technique of configuring, in the photomask, a surface being in contact with the stage device using a plurality of materials having coefficients of thermal expansion different from each other. In the technique disclosed in Japanese Patent Application Laid-Open No. 2010-182942, expansion occurred in the photomask during exposure processing can be suppressed by using differences in the degrees of expansion between a plurality of materials having different coefficients of thermal expansion.